Several previous studies have shown that .gamma.-aminobutyric acid is a major inhibitory transmitter of the central nervous system as reported, for example, by Y. Godin et al., J. Neurochemistry, 16 869 (1969) and that disturbance of the excitation and inhibition interplay can lead to diseased states such as Huntington's chorea (The Lancet, Nov. 9, 1974, pp. 1122-1123), Parkinsonism, schizophrenia, epilepsy, depression, hyperkinesis and manic depression disorders, Biochem. Pharmacol. 23, 2637-2649 (1974). Certain compounds are known to elevate brain levels of .gamma.-aminobutyric acid, for example, n-dipropylacetate (Simler et al., Biochem. Pharm. 22, 1701 (1973)) by competitively inhibiting .gamma.-aminobutyric acid transaminase resulting in a reversible effect which lasts for only about two hours. Also, 4-aminotetrolic acid (P. M. Beart et al., J. Neurochem. 19, 1849 (1972)) is known to be a competitive reversible inhibitor of .gamma.-aminobutyric acid transaminase. Also, .alpha.-vinyl- and .alpha.-acetylene-.gamma.-aminobutyric acids are disclosed respectively in U.S. Pat. Nos. 3,960,927, issued June 1, 1976, and 3,959,356, issued May 25, 1976, as irreversible inhibitors of .gamma.-aminobutyric acid transaminase.